Heating, ventilating, and air conditioning equipment has been used to heat, cool, and ventilate buildings and other enclosed spaces where people live and work. Air conditioning units and heat pumps have been used that have had single-speed motors driving the compressors. Such units operated at one speed and cycled on and off under the control of a thermostat to maintain space temperature, operating either at full speed, which was often noisy, or turned off.
In recent years, variable-speed drives have been used to drive compressors as well as indoor and outdoor fans. Examples include inverter-driven brushless DC compressors. Special thermostats have been used that have changed the speed of the compressor and fans to maintain the set point temperature rather than cycling on and off. Since these units usually operate considerably below maximum speed, and the heat exchanger sizes remain the same, energy consumption is reduced, resulting in greater overall efficiency.
Single-speed units have been replaced with variable-speed units, which has resulted in efficiency improvements as well as reductions in noise. In the past, however, such a unit replacement has necessitated the replacement of the thermostat, wiring between the unit and the thermostat, or both, which has resulted in a greater cost of replacement, especially in comparison with replacement with another single-speed unit that could reuse the old thermostat and thermostat wiring.
Two-speed or two-stage units (having two fixed non-zero speeds) have also been used which have had an additional wire from the thermostat to select between two non-zero compressor speeds, and often two non-zero fan speeds as well. Two-stage thermostats have typically called for stage one first, when the unit first turns on. In some configurations, the thermostat continued to call for stage one provided the measured temperature in the space moved towards the thermostat set point temperature. With such two-stage thermostats, however, if the measured temperature in the space moved away from the thermostat set point temperature, the thermostat called for stage two, increasing the capacity of the unit. In such configurations, the more-efficient and quieter stage one was used unless the cooling or heating demand became so large that the higher-capacity stage two was required in order to prevent the difference between the space temperature and the set point temperature from increasing.
In other two-stage configurations, however, the two-stage thermostat called for stage one if the measured temperature in the space was sufficiently close to the thermostat set point temperature, but called for stage two if the measured temperature in the space was sufficiently far away from the thermostat set point temperature. In such configurations, if the unit or system was left on and the set point temperature remained unchanged, the thermostat called for stage one first, and only increased to stage two if stage one was inadequate to keep the measured temperature in the space sufficiently close to the thermostat set point temperature. Again, in such configurations, in steady operation, the more-efficient and quieter stage one was used unless the cooling or heating demand became so large that the higher-capacity stage two was required in order to keep the temperature in the space sufficiently close to the set point temperature. When the operator first turned the unit on, however, or when the operator changed the set point temperature, the measured temperature in the space may have initially been sufficiently far away from the thermostat set point temperature so as to demand stage two capacity. Thus, this configuration typically resulted in more use of stage two, specifically, when the operator adjusted the thermostat. But the system or unit was typically more responsive to operator adjustments.
Three-speed units with an additional thermostat wire have also been used. Further, tandem multiple-capacity units have also been used with similar thermostats, which have had multiple single-speed compressors, for example. Such units have operated with one compressor running or with multiple (e.g., two) compressors in operation to provide different capacities. With two compressors, for instance, as many as three different capacities have been obtained where the two compressors were of different sizes or ran at different speeds. The indoor fan, outdoor fan, or both, have been operated at different speeds depending on which or how many compressors were in operation.
Two-speed or two-stage units and various other multi-capacity units have provided performance between that of single-speed units and variable-speed units, regarding efficiency and noise, but again, in order to replace a two-speed unit or another multi-capacity unit with a variable-speed unit, replacement of the thermostat and thermostat wiring was typically required. Further, when single-speed, two-speed, or other multiple-capacity units have been replaced with variable-speed units, for example, replacement of the indoor fan (i.e., blower), indoor fan motor, expansion valve, or a combination thereof, often needed to be replaced as well. In split systems, the complete indoor portion often needed to be replaced in order to convert to a variable-speed system, which often substantially increased cost.
Needs or potential for benefit exist for equipment and methods that allow single-speed and two-speed units (e.g., packaged units, spit system units, or just outdoor portions of split systems), as well as various multi-capacity units to be replaced with variable-speed units or units having more speeds than the preexisting system offered without requiring that the thermostat, thermostat wiring, indoor fan, indoor fan motor, or a combination thereof (e.g., among other things), be replaced as well. Further, needs or potential for benefit exist for equipment and methods that allow thermostats for discrete-speed (e.g., single-speed or two-speed) units to be used to control variable-speed HVAC units or units having more speeds without requiring that the thermostat, thermostat wiring, or both, be replaced.
In addition, in the past, discrete-speed units, and especially single-speed units, have often operated at a substantially higher capacity than necessary for the particular installation or the particular conditions present. This has resulted in a unit operating at a high speed for a short time rather than, more efficiently and less obtrusively, operating for a longer time at a lower speed. Consequently, needs or potential for benefit exist for equipment and methods that allow HVAC units to detect when it is appropriate to operate at a lower speed for a longer time and to automatically do so. Furthermore, since conditions under which HVAC units operate change over time, often in a fairly short time, needs or potential for benefit exist for equipment and methods that allow HVAC units to return to a higher speed when needed to maintain the set point temperature, and to automatically do so when appropriate.
Moreover, traditional discrete-speed heat pumps have been used for both cooling (e.g., in the summer) and heating (e.g., in the winter). Compressors have typically been operated at the same speed whether in the heating or the cooling mode, and heat pumps have typically had correspondingly similar capacity ratings whether in the cooling or heating mode. Even multiple-speed heat pumps and variable-speed heat pumps have traditionally operated at the same selection of (e.g., compressor motor) speeds, or over the same range of speeds, whether in the cooling or the heating mode.
In many climates, however, the demand for cooling or heating is substantially unequal, For example, in warm climates, there may be a much greater demand for cooling than for heating, and a heat pump that is selected to meet the demand cooling may be oversized in the heating mode. Such a unit may operate at a higher speed than needed in the heating mode, may cycle more frequently than desired, may be noisier than necessary, may be less efficient than optimal in the heating mode, or a combination thereof, as examples. On the other hand, in colder climates, there may be a much greater demand for heating than for cooling, and a heat pump that is selected to meet the demand heating may be oversized in the cooling mode. Such a unit may operate at a higher speed than needed in the cooling mode, may cycle more frequently than desired, may be noisier than necessary, may be less efficient than optimal in the cooling mode, or a combination thereof, as examples.
As an alternative, in colder climates, a heat pump can be sized to meet the cooling demand, and a supplemental heat source can be used when the heat pump is inadequate to meet demand in colder weather. Such a supplemental heat source may be, or include, electrical resistance heating, or a furnace, as examples. Electrical resistance heating, however, is not very efficient, and as a result, increases energy consumption. Further, adding a furnace substantially increases equipment cost.
As a result, needs or potential for benefit exist for equipment and methods of adapting and distributing heat pumps to provide improved efficiency performance, lower equipment cost, or both, in different climates where demand for cooling and heating are substantially unequal. In addition, needs or potential for benefit exist for heat pumps that are adapted to provide improved efficiency performance in different climates where demand for cooling and heating are substantially unequal.
Further, needs or potential for benefit or improvement exist for methods of manufacturing such heat pumps, HVAC equipment, and HVAC units, as well as systems and buildings having such devices. Other needs or potential for benefit or improvement may also be described herein or known in the HVAC or control industries. Room for improvement exists over the prior art in these and other areas that may be apparent to a person of ordinary skill in the art having studied this document.
References that may provide useful background information include WO 2008/097743 (Chen et al.; PCT/US2008/052110), and US 2008/0041081 (Tolbert; Ser. No. 11/464,586).
These drawings illustrate, among other things, examples of embodiments of the invention. Other embodiments may differ.